y^2-9x^2+6x-1=（y^2-1）+( )=y^2-( )=6x-1-( )

2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 先化简再求值 x(9x-y)-y(y-x)+(x-y)的平方,其中x=-1,y=2 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 解二元一次方程 {3(x+y)-4(x-y)=-9 x+y/2+x-y/6=1 常微分方程的通解dy/dx=(x-y+1)/(x+y-3)y^4=2y^n+y=0y''+6y'+9y=e^(-3x)y''+y'-2y=4e^(2x) 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. (x+y)(x-y)+(x-y)^2-(6x^2×y÷2y-2xy^2÷2y)其中x=-3,y=1/3 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 [(-x-y)(-x+y)-(x+y)^2-x(y-y^2)}÷1/2y 9y=3x-(x-1),4(x+y)-(2x+4)=8y 解二元一次方程组：3(x+y)-4(x-y)=4,x+y/2+x-y/6+1x+y/2+x-y/6+1=1 化简求值:(x+y)+(2x+1/2y)+(3x+1/6y)+.+(9x+1/72y) ,其中x=1,y=-9 9xy(x-y)(x+1)-3y(x-y)(3x+2y)+6y的平方(x-y)(x+1),因式分解